Tracker server is a reference point for all Sync clients. When looking for other peers for particular folder, each client connects to the Tracker and asks it to:
a) let all other peers with same folder id know where it is
b) get the list of IPs:ports for all peers with same folder id.
All instances of Sync always know 4 BitTorrent public Tracker servers and automatically attempt to connect there if allowed. Their IPs are 18.104.22.168, 22.214.171.124, 126.96.36.199, 188.8.131.52, port 3000.
While there is no any private or insecure data sent to the Tracker servers, many companies prefer to have their own Tracker server inside their local network. In this case, the administrator will need to setup his own Tracker server and configure Sync clients to connect to it instead of BitTorrent Trackers.